1. Field of the Invention
This invention relates to improvements in the process of preparation of beta-diketones and in particular to the production of 1-phenylisodecane-1,3-dione by the alkaline condensation of acetophenone and an ester of an alkanoic acid.
2. Statement of Related Art
U.S. Pat. No. 4,175,012 to Kenneth MacKay et al., describes the preparation of beta-diketones which are useful as metal extractants. The diketones have the formula ##STR1## where R is phenyl or alkyl substituted phenyl, R' is alkyl, alkyl substituted phenyl or chloro substituted phenyl, and R" is H or CN. The products are prepared by the reaction of a compound having an acetyl moiety and a lower alkyl ester in the presence of sodium hydride and an inert organic solvent.
In recent time the beta-diketone, 1-phenyl isodecane-1,3-dione has been prepared by the alkaline condensation of acetophenone and a lower alkyl ester of an alkanoic acid such as methyl isooctanoate in an inert organic solvent media. In the reaction some of the methyl isooctanoate is converted to sodium isooctanoate. When the reaction is completed, the reaction mixture is acidified, typically in a separate reactor which contains excess sulfuric acid, whereby the sodium salts are acidified. The resultant acidified organic phase is then washed several times with water, and the diketone product recovered by stripping the volatiles from the organic and distilling the residue at reduced pressure.
The foregoing process, however, has some disadvantages which results in low yields and some residual degradation products. These result from the fact that the diketone product is thermally cleaved in the presence of alkali to a carboxylic acid and a methyl ketone degradation product. Accordingly it is desirable that the process be improved so that yield of product is maximized and the formation of degradation products is minimized.